Electrical resistance alloy



Patented Aug. 25, 1942 ELECTRICAL RESISTANCE ALLOY Victor 0. Allen,Madison, and Joseph Elolak, Newark, N. J.-, assignors to WilburB..Driver Company, Newark, N. 3., a corporation of New Jersey NoDrawing. Application March 30, Serial N0. 436,912

'Claims. (c1. 75-i71) This invention relates to electrical resistancealloys and has for its object theprovision of a high resistance alloyhaving a relatively low temperature coefficient of, resistivity,particularly in the range of temperatures below' about Another object isto provide an electrical resistance alloy suitable for use as a resistorele-' ment in electrical devices, apparatus and circuits.

Still another object is to provide an electrical resistance alloyconsisting predominately of of the alloy .at any temperature rangeC.-300 C.

about 5%, will effectively lower the temperature coeflicient ofresistivity of the nickel-chromium alloy from the normal value of .00014ohm to.

a value as low as .00002, and will at the same time markedly increasethe electrical resistance within the In general, the copperand aluminum'additions to the alloy are made at the ei rpense of the nickel contentof the alloy and may be added in various percentages; within the rangesabove nickel and containing chromium 10% to 30% in which the normalelectrical resistance is materially increased and the temperaturecoefilcient of resistivity is materially lowered without material lossof hot and cold workability.

Other objects and advantages will be apparent as the invention is morefully hereinafter disclosed.

-In accordance with these objects, we have discovered that copper andaluminum, incombination', are particularly effective, in alloys ofnickel and chromium, as agents for increasing the electrical resistanceof the alloy and for lowering the temperature coemcient of resistivityand that, in general, copper in amounts up to-3%' and Al in totalamounts up to 5%,

but Cu and Al combined in total amount not over about 6% may be employedfor this purpose without seriously impairing the normal hot and coldworkabilityoi the'base nickel-chromium alloy.

-As one specific embodiment of the present'invention, but not as alimitation thereof, the adaptation of the'same to a well knownnickelchromium alloy containing-80% Ni and 20% Cr heretofore employed asan electric resistance alloy will he described. a

The normal temperature coeflicient of regiven and in different relativeproportions to obtain a plurality ofhigh resistance alloys ofprogressively lower temperature coefflcients of resistivity anddifierent electrical resistances.

A copper content muchin excess of about 3% is undesirable for the reasonthat the hot workability of the alloy is detrimentally efiected. An

' Al content of much over 5% is undesirable for the reason that both thehot and cold workability of the alloy is deterimentally effected. -A

total amount of over about 6% of the two constituents (Al and Cu) isundesirable for the reason that cold drawing properties of the alloy,especially at small diameters, appears detri-' mentally eflected.

The following three (3) examples of the present invention areillustrative of the effect of variation of Al and Cu within the rangesgiven on the electrical resistance and the temperature coeflicient ofresistivity of the base Cr-Ni alloy employed:

(1) An alloy containing Al 4%, Cu 2%, Cr

20% and Ni 74%.

alloy, in wireform, has an electrical resistance of about 900 ohms percircular mil toot at 20 C. and has a temperature coeflicient ofresistivity of .00000'7 ohm per ohm per degree centigrade;

sistivity 0'1 a nickel-chromium alloy containing 80% Ni and 20% Crwithin the temperature range 20-100 C. is .00014 ohm per ohm per degreecentigrade, and the electrical resistance at 20 C. approximates 650 ohmsper circular mil .foot (C. M. F.). The temperature coemcient ofresistivity of thisalloy is too high for use as a resistor element inhigh accuracy electrical de-, vices, apparatus and circuits. It isdesired by the practice of the presentinvention to lower the temperaturecoeflicient oi resistivity of this alloy to a value below .0001 1 ohm.We have discovered that copper and aluminum additions to this alloy intotal amount not over about 6% Q. fact at 20 C. and has a temperaturecoefllcie'nt I centigrade. Alloy #3, above, as far as its temperatureco- (2) An alloy containing Al 4%, cu Cr 20%, and Ni 75.50%.

This alloy, in wire form, has an electrical resistance 01' about 800ohms per circular mil toot at -20" C. and has a temperature coefliciento! resistivity of .00004 ohms per ohm per degree centig'rade.

(3) An alloy containing Al 3%,v Cu 3%, Cr 20% and Ni 74%.

- This alloy,flin wire form, has an electrical resistance or about 7'75ohmsper circular mil oi resistivityof .00002 ohm per ohm per degree withcopper not over about 3% and A1 not over ei'flcient of resistivity isconcerned is equal to the usual type of Gum and Cu-Mn-Ni resistor alloysheretofore employed in electrical devices, apparatus and circuits, suchas those known in the art as Cupron (Cu 55%; Ni 45%) and Manganin (Cu84%; Mn 12%; Ni 4%) but has an electrical resistance of 7'75 as comparedto an' electrical resistance of about 290 for these old types of alloys.

Alloy #1, as far as its temperature coeflicient of resistivity isconcerned is far better than the well known Fe'Cr-AI alloy known in theart as ohmaloy containing 80% Fe, 15% Cr and Al, and has a materiallyhigher electrical resistance, with the added advantage that alloy #1 isaustenitic in structure and is non-magnetic. It, therefore, is ofgreater utility for use as radio resistor elements than is the: Ohmaloyalloy.

Alloy #2 is about half as good as alloy #3 insofar as its temperaturecoefiicient of resistivity is concerned, but its materially higherelectrical resistance over either Cupron or Manganin places it in aposition to be preferred over these alloys as instrument and radioresistors, shunts and in various types of thermocouples.

In the manufacture of the above alloys, the Al lieved apparentthat theCr may be varied within the range to 30% with resultant increase ventionand the three specific embodiments thereof, it is believed apparent thatthe same may be widely varied without essential departure therefrom andallsuch are contemplated as may fall within the scope of the followingclaims.

What we claim is:

1. An electrical resistance alloy consisting of chromium 10 to 30%, Alfrom small fractional percentages up to about 5%, Cu from smallfractional percentages up to about 3%, with the total Al and Cu not overabout 6%, balance nickel.

2. An electrical resistance alloy consisting of chromium about Al fromsmall fractional percentages up to about 5%, Cu from small fractionalpercentages up to about 3%, with the total Al and Cu not over about 6%,balance nickel.

3. An electrical resistance alloy consisting of ch1'omium 20%, Al 4%, Cu2%, balance Ni.

4. An electrical resistance alloy consisting of Cr 20%, Al 4%, Cu 50%,balance Ni.

5. An electrical resistance alloy consisting of Cr 20%, Al 3%, Cu 3%,balance Ni.

VICTOR O. ALLEN. JOSEPH F. POLAK.

